JP2009144242A - Method for improving uniformity and adhesiveness of low-resistivity tungsten film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for improving uniformity and adhesiveness of a tungsten film having a low resistivity. <P>SOLUTION: The low-resistivity tungsten film is formed by exposing a tungsten nucleation layer to a series of reducing agent pulses before depositing a tungsten bulk layer. According to various embodiments, the method involves the reducing agent pulses with different flow rates, different pulse times and different interval times. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for preparing a tungsten film. Embodiments of the present invention are particularly useful for integrated circuit applications that require tungsten thin films with low electrical resistivity and excellent uniformity and adhesion.

  The deposition of tungsten films using chemical vapor deposition (CVD) is an integral part of many semiconductor manufacturing processes. The tungsten film can be used as a horizontal interconnect in the silicon substrate, adjacent metal interlayer vias, and a low resistivity electrical connection formed as a contact between the first metal layer and the device. In a conventional tungsten deposition process, the wafer is heated to the process temperature in a vacuum chamber, and a very thin portion of the tungsten film that becomes the seed or nucleation layer is deposited. Thereafter, the remaining portion (bulk layer) of the tungsten film is formed on the nucleation layer. Conventionally, a tungsten bulk layer is formed on a growing tungsten layer by reducing tungsten hexafluoride (WF6) with hydrogen (H2). A tungsten bulk layer is generally deposited faster than a nucleation layer, but it is difficult to reliably form without first forming a nucleation layer.

  Advances in technology require maintaining very low resistivity while making tungsten electrical connections increasingly thinner. Therefore, it is important to realize a tungsten film having an ultra-low resistivity by a tungsten deposition process. In order to improve the yield while increasing the size of the wafer, the uniformity of the coating properties of the entire wafer is also important.

  Provided is a method for forming a low resistivity tungsten film having excellent uniformity and good adhesion to a lower layer. The low resistivity tungsten film is formed by exposing the tungsten nucleation layer to a reducing agent prior to depositing the tungsten bulk layer. For example, by exposing the tungsten nucleation layer to a number of successive reducing agent pulses instead of a single reducing agent pulse, a tungsten film having good uniformity and adhesion and low resistivity is formed.

  In one aspect of the invention, the tungsten film is formed by exposing the tungsten nucleation layer to a pulse of reducing agent prior to depositing the tungsten bulk layer. The steps of depositing the tungsten film include (a) a step of placing a substrate in the reaction chamber, (b) a step of depositing a nucleation layer of tungsten on the substrate, and (c) a plurality of steps without pulse operation between pulses. And (d) depositing a tungsten bulk layer on the tungsten nucleation layer to form a tungsten film.

  In some embodiments of the method according to the above sequence, the reducing agent is a boron-containing reducing agent, and in some embodiments, the reducing agent is diborane. In some embodiments, the number of reducing agent pulses in step (c) is 2 to 8. In a further embodiment, the substrate is heated from about 375 ° C. to 415 ° C. before it is exposed to the reducing agent pulse to stabilize the temperature. In some embodiments, the substrate is heated from about 375 ° C. to 415 ° C. prior to depositing the tungsten bulk layer on the tungsten nucleation layer. In some embodiments, the nucleation layer is exposed to a tungsten-containing precursor prior to depositing a tungsten bulk layer on the tungsten nucleation layer.

  According to various embodiments of the tungsten film formation process, each pulse of the plurality of reducing agent pulses in step (c) has a pulse time, which is 0.5 to 5 seconds. The pulse time can vary between reducing agent pulses. In some embodiments, the interval time between reducing agent pulses is about 2 to 5 seconds. The interval time between reducing agent pulses may vary depending on the interval. In some embodiments, the interval time between reducing agent pulses is shorter for subsequent pulses. In a further embodiment, each pulse of the plurality of reducing agent pulses has a flow rate that is between about 100 and 500 sccm. The flow rate can also vary between reducing agent pulses.

  In some embodiments of the above method, a 500 Å thick tungsten film formed on the substrate has a sheet resistance non-uniformity of less than 5% and / or a resistivity of 12 micro ohm centimeters. Is less than.

  In another embodiment, the tungsten film deposition process comprises: (a) placing a substrate in a reaction chamber; (b) depositing a nucleation layer of tungsten on the substrate by a pulse nucleation layer process; c) heating the substrate to about 395 ° C. and stabilizing the temperature; and (d) maintaining the substrate temperature at about 395 ° C. while maintaining the substrate temperature at about 395 ° C. without pulsing between pulses, Exposing to diborane; (e) maintaining the substrate temperature at about 395 ° C .; (f) exposing the nucleation layer to a tungsten-containing precursor; and (g) forming a tungsten bulk layer on the tungsten nucleation layer. The diborane has a flow rate of about 100 to 500 sccm, a pulse time of about 0.5 to 5 seconds, and an interval time of about 2 to 5 seconds.

  In one embodiment of an apparatus for depositing a tungsten film on a substrate, the apparatus comprises a multi-station substrate deposition chamber and a controller that controls operation within the multi-station deposition chamber. The multi-station substrate deposition chamber has a tungsten nucleation layer deposition station, a reducing agent exposure station, and a tungsten bulk layer deposition station. The controller controls the alternating generation of the reducing agent pulse and the tungsten-containing precursor pulse at the tungsten nucleation layer deposition station to deposit the nucleation layer, and the plurality of reducing agent pulses are applied within the reducing agent exposure station. All or part of the tungsten bulk layer is deposited by exposing it to a tungsten-containing precursor and a reducing agent in a tungsten bulk layer deposition station, generated without pulsing between pulses. In certain embodiments, the controller controls the transfer of the substrate from the tungsten nucleation layer deposition station to the reducing agent station and from the reducing agent station to the tungsten bulk layer deposition station.

  These and other features of the present invention are described in detail below with reference to the accompanying drawings.

  The following detailed description will be better understood when considered in conjunction with the drawings.

6 is a graph representing reducing agent pulse and interval time in various embodiments of the present invention.

6 is a graph representing reducing agent pulse and interval time in various embodiments of the present invention.

6 is a graph representing reducing agent pulse and interval time in various embodiments of the present invention.

It is a graph which shows the tungsten film sheet resistance in the wafer for tungsten films formed by the single pulse and the multipulse reducing agent process.

6 is a graph showing sheet resistance non-uniformity versus resistivity for multiple tungsten films formed by single pulse and multi-pulse reducing agent treatment.

6 is a process flowchart illustrating related operations or methods in various embodiments of the invention.

6 is a process flowchart illustrating related operations or methods in various embodiments of the invention.

6 is a process flowchart illustrating related operations or methods in various embodiments of the invention.

1 is a block diagram of a processing system suitable for performing a tungsten deposition process in embodiments of the present invention. FIG.

It is the schematic of the laminated film containing the tungsten nucleation layer and tungsten bulk layer which were formed in several embodiment of this invention.

It is the schematic of the laminated film containing the tungsten nucleation layer and tungsten bulk layer which were formed in several embodiment of this invention.

  In the following description, numerous specific details regarding the formation of tungsten films are set forth in order to provide a thorough understanding of the present invention. A preferred method includes subjecting the tungsten nucleation layer, described in detail below, to a reducing agent pulse. Modifications, adaptations, or changes to the specific methods and structures shown herein will be apparent to those skilled in the art and are within the scope of the present invention.

  In general, the nucleation layer is a thin conformal layer that facilitates the formation of the next bulk layer thereon. An efficient tungsten deposition process requires a tungsten nucleation layer, which typically has a higher electrical resistivity than the tungsten bulk layer. Therefore, in order to keep the electrical resistivity of the entire tungsten film (tungsten nucleation layer and tungsten bulk layer) low, the tungsten nucleation layer must be kept as thin as possible. On the other hand, the tungsten nucleation layer must also be thick enough to completely cover the underlying substrate and support high quality bulk deposition.

  Resistivity is an intrinsic property of a material and is a measure of the material's resistance to charge transfer through the material. The resistivity of the material affects the electrical operation of the integrated circuit. The low resistivity tungsten film minimizes power loss and overheating in integrated circuit designs. Furthermore, it is desirable that the tungsten film is excellent in uniformity of resistivity in the wafer and excellent in adhesion to the lower layer material.

  The method described herein includes forming a tungsten film with a tungsten nucleation layer. In certain embodiments, the nucleation layer is exposed to a reducing agent pulse prior to depositing the tungsten bulk layer. The resulting tungsten film generally has a lower resistivity, better uniformity and better adhesion than a tungsten film formed without exposing the nucleation layer to the reducing agent pulse.

In the following, aspects of certain embodiments of the present invention will be described in further detail.
[process]

  In the process described herein, the tungsten nucleation layer is exposed to one or more reducing agent pulses before the tungsten bulk layer is deposited on the tungsten nucleation layer. This may be regarded as a nucleation layer surface treatment. Exposure to the reducing agent pulse improves the resistivity of the entire tungsten film (nucleation layer and bulk layer).

  FIG. 1A represents a single reducing agent pulse to the tungsten nucleation layer. The vertical axis represents gas flow and the horizontal axis represents time divided into stages associated with various steps of the process. After the tungsten nucleation layer is deposited on the substrate, it is exposed to a single reducing agent pulse as shown in FIG. 1A. A tungsten bulk layer is then deposited on the nucleation layer (not shown). In the example shown in FIG. 1A, diborane is used as the reducing agent, but other reducing agents such as silane and other boranes may be used.

In general, the tungsten film formed after the nucleation layer is subjected to the reducing agent treatment has a low resistivity, but the uniformity of the sheet resistance is tungsten formed without exposing the nucleation layer to the reducing agent. It is inferior to the film (ie, the percentage of non-uniformity is high). Of a 500 Å thick tungsten film formed using (a) a single reducing agent pulse as shown in FIG. 1A and (b) not exposing the nucleation layer to the reducing agent. Typical resistivity and percent non-uniformities are shown in Table 1 below.
Table 1: Typical resistivity and uniformity of a 500 angstrom thick tungsten film formed with and without a reducing agent in the nucleation layer

  As shown in Table 1, the typical resistivity of a tungsten film formed without a reducing agent treatment is that of a film formed using a single reducing agent pulse as shown in FIG. 1A. Greater than. However, the sheet resistance uniformity of tungsten films formed without reducing agent treatment is generally superior to the sheet resistance uniformity of films formed by single pulse reducing agent treatment. The resistivity of tungsten films formed by single pulse reducing agent treatment can be further reduced by exposing more to the reducing agent (ie, increasing the pulse time and / or increasing the gas flow). Although, the adhesion of the tungsten film to the underlying layer (not shown in Table 1) is reduced by extensive exposure to a single pulsed reducing agent.

  FIG. 1B is a graph representing the reducing agent pulse and the interval time in a particular embodiment of the invention. The vertical axis represents gas flow and the horizontal axis represents time divided into stages associated with various steps of the process. The deposited nucleation layer is exposed to a multi-reducing agent pulse with an interval time between pulses. During the interval, no reducing agent is supplied to the reaction chamber, as shown in FIG. 1B. As described above, the reducing agent in this example is diborane, but other reducing agents may be used.

The multi-pulse process as shown in FIG. 1B unexpectedly improves the resistivity and uniformity of the tungsten film. Table 2 shows the properties of a tungsten film about 510 angstroms thick deposited on a titanium nitride barrier layer on a 300 mm wafer. The reducing agent used for the reducing agent treatment was diborane. The amount of diborane exposure to each wafer is equal, i.e. 1 pulse for 6 seconds and 6 pulses for 1 second, both exposed to diborane for 6 seconds. Resistivity, percent non-uniformity, and adhesion were measured. Adhesion was measured by a scribe / tape test. In the scribe / tape test, the tungsten film was drawn with a diamond cutter, the tape was applied to the drawn area, and then the tape was peeled off. If a tungsten film remains in the titanium nitride barrier layer after the scribe / tape test, this indicates that the adhesion is “pass”. On the other hand, if the tungsten film is partially removed by the tape, it indicates “fail”. As can be seen from the data, the multi-pulse diborane treatment of the tungsten nucleation layer has a lower resistivity and better sheet resistance uniformity (ie, less uniformity) while maintaining higher adhesion than with single pulse treatment. A tungsten film (with a low percent uniformity) is obtained.
Table 2: Comparison of 510 Å thick tungsten films in a titanium nitride barrier layer on a 300 mm wafer prepared using a single pulse reducing agent treatment and a multi-pulse reducing agent treatment.

  As described in detail below with reference to FIGS. 2 and 3, as shown in Table 2, the resistivity and uniformity of the tungsten film is unexpected while maintaining excellent adhesion by using different pulses of diborane. To improve. As noted above, the total diborane exposure for each wafer in Table 2 is equal. The only difference between multi-pulse processing and single-pulse processing shown in Table 2 is that multi-pulse processing is subdivided into smaller pulse diboranes, further increasing the resistivity and uniformity. It is to be seen.

  FIG. 2 is a graph showing tungsten film sheet resistance in a tungsten film wafer formed by single-pulse and multi-pulse reducing agent treatment. The data shown in this graph was obtained from the same wafer taken in Table 2. As can be seen from the data, the multi-pulse diborane process lowers the resistivity at both the wafer edge and wafer center and reduces the difference in resistivity between the center and edge. Thus, multipulse diborane processing has both a low resistivity and non-uniformity percentage compared to single pulse processing.

  FIG. 3 is a graph showing the relationship between the sheet resistance non-uniformity and the resistivity of a number of tungsten films formed by single pulse and multi-pulse reducing agent treatment. Tungsten films, indicated by data points, were deposited on different barrier layer materials, and the tungsten nucleation layer was treated with different gas streams. Although there are variations among the tungsten films, the tungsten film formed by the multi-pulse reducing agent treatment exhibits characteristics superior to the film formed by the single pulse treatment. All of the multi-pulse processed films enclosed in an ellipse on the graph have a low percentage of sheet resistance non-uniformity and low resistivity. The adhesion results in the multipulse treatment were also good, and only one tungsten film was rejected. On the other hand, tungsten films formed by single pulse reducing agent treatment generally have a high percentage of sheet resistance non-uniformity or high resistivity. One single pulse reducing agent-treated film (data point in the ellipse) with a low percentage of sheet resistance non-uniformity and low resistivity fails the adhesion.

  The reducing agent gas flow rate in one pulse is preferably about 100 to 500 sccm. The pulse time of each reducing agent pulse varies between about 0.5 seconds and 5 seconds, and more preferably is about 1 to 2 seconds. The interval time between each reducing agent pulse of the plurality of reducing agent pulses is preferably about 2 to 5 seconds. Under these operating conditions, the number of reducing agent pulses is preferably between 2 and 8. The chamber pressure may vary widely during multi-pulse reducing agent treatment and is about 2 to 100 Torr, more preferably about 20 to 40 Torr. These reducing agent pulse parameters are based on a 300 mm wafer and need to be adjusted according to the size of the wafer, the specific processing apparatus, the specific reducing agent used, and the like. After exposure to the reducing agent pulse, a tungsten bulk layer is deposited on the nucleation layer. The resulting tungsten film has low resistivity, good sheet resistance uniformity, and strong adhesion compared to a thin film formed by exposing the nucleation layer to a single reducing agent pulse.

  It has been found that there is an optimal number of pulses that should be used to obtain the desired tungsten film properties depending on the pulse time, pulse dose, and interval time. If too few pulses are used, both the resistivity of the tungsten film and the non-uniformity of the sheet resistance increase. If too many pulses are used, the resistivity and non-uniformity of the tungsten film will be low, but the adhesion will be weak. In many embodiments, the optimal number of pulses is between 2 and 8, depending on the operating conditions used. A very large number of pulses can be used for very different processing conditions.

  In embodiments where the tungsten nucleation layer is exposed to multiple pulses, the pulses may be the same or different from each other. FIG. 1C shows an example of a graph representing different reducing agent pulses and interval times in certain embodiments. As noted above, the vertical axis represents gas flow and the horizontal axis represents time divided into stages associated with various steps of the process. In FIG. 1C, the pulse time of the reducing agent pulse is different and is shorter for the subsequent pulses. Moreover, in FIG. 1C, the gas flow rate in each reducing agent pulse is different, and decreases with the subsequent pulse. Furthermore, in FIG. 1C, the interval time between pulses is different and is shorter for subsequent pulses. The reducing agent pulse time, reducing agent gas flow rate, and interval time are varied separately to optimize throughput and further improve the resistivity, uniformity, and adhesion of the tungsten film.

  For example, changes in pulse flow rate, pulse time, and / or interval time can be due to different adsorption rates of reducing agent on the substrate surface. In certain embodiments, the pulse time and / or flow rate may be reduced, in which case there is no significant loss of substrate reducing agent coverage and throughput is improved. In the example in FIG. 1C, the flow rate, pulse time, and interval time are all decreasing, but may be decreased, increased, or changed individually. In certain embodiments, for example, two flow rates and / or pulse times are used, one for the first pulse and one for all subsequent pulses.

  FIG. 4 is a flowchart illustrating the flow of one process in a specific embodiment of the present invention. First, as shown in process block 401, a substrate is provided and placed in a reaction chamber. In many embodiments of the invention, the substrate is a semi-finished electronic device (eg, a semi-finished integrated circuit). In some embodiments, the substrate may be coated with a titanium nitride layer (e.g., deposited by physical vapor deposition (PVD) using titanium tetrachloride or chemical vapor deposition (CVD)). A tungsten nucleation layer is deposited on this layer.

  Next, as shown in process block 403, a tungsten nucleation layer is deposited on the substrate. In certain embodiments, a pulse nucleation layer (PNL) process is used to deposit a tungsten nucleation layer. In the PNL deposition process, pulses of reducing agent, purge gas, and tungsten-containing precursor are sequentially sent into and out of the reaction chamber. This process is repeated periodically until the nucleation layer has the desired thickness. PNL is similar to the atomic layer deposition (ALD) technique reported in the literature, but with a higher operating pressure range (greater than 1 Torr), a higher growth rate per cycle (one monolayer per cycle). It is generally distinguished from ALD by greater than film growth. The PNL process picked up herein also includes a conventional ALD type process.

  As described above, the tungsten nucleation layer is a thin conformal layer that facilitates the growth of a tungsten bulk layer. The thickness of the tungsten nucleation layer is typically 10 to 30 angstroms. Further discussion of PNL-type processes for depositing tungsten nucleation layers can be found in commonly assigned US patent application Ser. No. 11 / 265,531, which is hereby incorporated by reference in its entirety. Further discussion of PNL-type processing can be found in commonly assigned US Pat. Nos. 6,844,258, 7,005,372, and 7,141,494, each of which is incorporated by reference in its entirety Is incorporated herein by reference. Additional methods of forming a tungsten nucleation layer can be found in commonly assigned US Pat. No. 6,905,543, which is incorporated herein by reference in its entirety.

  The next process operation 405 in FIG. 4 includes exposing the nucleation layer to a reducing agent pulse. In certain embodiments, the reducing agent is diborane. Diborane and related components have been found to adsorb well on metal nitride surfaces such as titanium nitride. Borane is not adsorbed on the substrate due to its own restrictions. Diborane reacts with the substrate surface and decomposes into a boron film. As long as the substrate continues to be exposed to diborane, the reaction can proceed. Therefore, the amount of adsorbed species depends on the amount of diborane exposed. In general, diborane is supplied from a diluted source (eg, diborane 5%, nitrogen 95%). Diborane may be sent to the reaction chamber using other additional carrier gases such as, for example, argon, hydrogen, and / or silane. Embodiments also include an inert gas / hydrogen gas mixture that continues to flow into the reaction chamber during both the reducing agent pulse and the interval time. In certain embodiments, the inert gas is argon. However, during the interval time, a continuously flowing inert gas / hydrogen gas mixture, or gases other than background gas, do not flow into the reaction chamber, i.e. any pulse during the interval time between reducing agent pulses. There is no operation. The time that the nucleation layer is exposed to the reducing agent varies based in part on the amount of exposure and the chamber conditions. As described above with reference to FIG. 1C, the reducing agent pulse time, interval time, and flow rate may all vary.

  After the tungsten nucleation layer is exposed to the reducing agent pulse, a tungsten bulk layer is deposited thereon as shown in operation 407. In many embodiments, the tungsten bulk layer is deposited using a CVD process. This is because CVD is known to quickly form a low resistivity film. Any suitable CVD process with any suitable tungsten-containing precursor can be utilized. In certain embodiments, the tungsten precursor is one of WF6, WCl6, and W (CO) 6. The CVD process is often performed using a mixture of molecular hydrogen and one or more of the above precursors. In other embodiments, the CVD process may use a tungsten precursor with silane, a mixture of hydrogen and silane, or a mixture of hydrogen and borane (eg, diborane). The tungsten bulk layer may be formed using methods other than CVD processes including ALD, PNL, or PVD.

  The tungsten bulk layer can be deposited to any thickness. The total thickness of tungsten interconnect lines for integrated circuit applications (tungsten nucleation layer and tungsten bulk layer) can be about 20 to 1,000 angstroms. In a typical bit line, the total thickness of the tungsten film is typically less than about 500 angstroms. After the tungsten film is deposited to a sufficient thickness, the process flow of FIG. 4 ends. In certain embodiments, operations 405 through 407 are repeatedly performed to deposit the tungsten film evenly.

  The flowchart of FIG. 5 shows another embodiment of the present invention for forming a tungsten film. The process flow in FIG. 5 is similar to the process flow in FIG. 4 except for operations 505, 509, and 511 that may optionally be performed in implementing the process flow in FIG.

  Similar to the process shown in FIG. 4, a substrate is first provided and placed in the reaction chamber, as indicated by process block 501. Next, as shown in process block 503, a tungsten nucleation layer is deposited on the substrate.

  As shown in process block 505, the substrate is optionally heated to about 375 ° C. to 415 ° C., preferably about 395 ° C., before the nucleation layer is exposed to the plurality of reducing agent pulses in process operation 507, The temperature is stabilized. Next, in process operation 507, the nucleation layer is exposed to a plurality of reducing agent pulses as described above. Next, in process operation 509, heat treatment is performed. In this heat treatment, the substrate can be heated to about 375 ° C. to 415 ° C., preferably 395 ° C. A preheat process operation 505 is performed before the nucleation layer is exposed to the reducing agent pulse (process operation 507), and a heat treatment process operation 509 is performed after the reducing agent treatment to obtain a tungsten film having better properties. It is done. The heat treatment operation may include a soak at 395 ° C. Pre / post heat treatment enhances film adhesion and reduces the percent of sheet resistance non-uniformity. The process temperature in the examples described herein is 395 ° C., but the other / post heat treatment may use other process temperatures.

  Also, in process operation 511, other portions of the tungsten nucleation layer may be formed by exposing the nucleation layer to a tungsten-containing precursor before the tungsten bulk layer is deposited on the nucleation layer. Any suitable tungsten-containing precursor can be used. In certain embodiments, the tungsten precursor is one of WF6, WCl6, and W (CO) 6. The tungsten-containing precursor is typically provided in a diluent gas such as argon, nitrogen, hydrogen, or combinations thereof. According to various embodiments, the temperature from blocks 505 to 511 may be constant or may vary between different temperatures from about 250 to 415 ° C. In certain embodiments, the substrate temperature may be below about 350 ° C., for example, about 250 ° C. to 350 ° C., or 275 ° C. to 350 ° C. The amount of tungsten-containing precursor exposure and the time the substrate is exposed to the precursor will vary depending on a number of factors. This process operation also improves the properties of the tungsten film.

  FIG. 6 shows a specific embodiment of the method shown in FIG. First, as shown in process block 601, a substrate is provided and placed in a reaction chamber. Next, as shown in process block 603, a tungsten nucleation layer is deposited on the substrate by a pulse nucleation layer process at a low temperature of about 300 ° C. As shown in process block 605, the substrate is heated to about 395 ° C. to stabilize the temperature. Thereafter, as described above, in process operation 607, the nucleation layer is exposed to a plurality of diborane pulses. Next, in process operation 609, the substrate is heat treated at about 395 ° C. Thereafter, in process operation 611, the nucleation layer is exposed to a tungsten-containing precursor. Any suitable tungsten-containing precursor may be provided, typically in a diluent gas. In certain embodiments, the tungsten precursor is one of WF6, WCl6, and W (CO) 6. The substrate temperature may be about 250 ° C. to 415 ° C., and in certain embodiments may be below about 350 ° C., for example, about 250 ° C. to 350 ° C., or 275 ° C. to 350 ° C. After the tungsten nucleation layer is exposed to the tungsten-containing precursor, in operation 613, a tungsten bulk layer is deposited over the tungsten nucleation layer.

As described above, the tungsten nucleation layer generally has a higher electrical resistivity than the tungsten bulk layer. In order to keep the resistivity of the entire tungsten film (tungsten nucleation layer and tungsten bulk layer) low, the thickness of the tungsten nucleation layer must be kept as thin as possible. As shown in FIG. 6, a PNL tungsten deposition process is used to form a thin nucleation layer. The nucleation layer is subjected to a multi-pulse reducing agent treatment before the tungsten bulk layer is deposited. The resulting tungsten film has low resistivity and excellent uniformity while maintaining good overall adhesion.
[apparatus]

  The method of the present invention may be performed in various types of deposition equipment available from various vendors. Examples of suitable devices are the Novellus Concept 2 Altus, the Concept-2 Altus-S, the Concept 3 Altus deposition system, all available from Novellus Systems, Inc., Santa Clara, California. Or any other commercially available CVD processing system. In some cases, the process may be performed sequentially at multiple deposition stations. See, for example, US Pat. No. 6,143,082, which is incorporated herein by reference. In some embodiments, the tungsten nucleation layer deposition process is a first station that is one of two, four, five, or more deposition stations disposed within a single deposition chamber. Or executed at the first and second stations. The reducing gas and the tungsten-containing gas are alternately introduced into the semiconductor substrate surface at the first station using a separate gas supply system that creates a local atmosphere on the substrate surface.

  FIG. 7 is a block diagram of a CVD processing system suitable for performing a tungsten thin film deposition process in embodiments of the present invention. System 700 includes a transfer module 703. The transfer module 703 minimizes the risk of contamination of the substrate being processed as it moves between the various reactor modules by providing a clean, pressurized atmosphere. The transfer module 703 mounted in the multi-station reactor 709 can perform PNL deposition, multi-pulse reducing agent treatment, and CVD in the embodiment of the present invention. The chamber 709 includes multi-stations 711, 713, 715, and 717 that can continuously execute these operations. For example, chamber 709 can be configured such that station 711 performs PNL deposition, station 713 performs multi-pulse reducing agent processing, and stations 715 and 717 perform CVD.

  One or more single or multi-station modules 707 that can be mounted on the transfer module 703 can perform plasma or chemical (non-plasma) preclean. The module can be used for a variety of other processes such as a post liner tungsten nitride process. The system 700 includes one or more (in this case, two) wafer source modules 701, where wafers are stored before and after processing. An atmospheric robot (not shown) in the atmospheric transfer chamber 719 first moves the wafer from the source module 701 to the load lock 721. A wafer transfer device (generally a robot arm unit) in the transfer module 703 moves the wafer from the load lock 721 to a module attached to the transfer module 703.

  In certain embodiments, a system controller is used to control process conditions during deposition. A controller is generally assumed to include one or more memory devices and one or more processors. The processor may include a CPU, computer, analog and / or digital input / output connection, stepper motor controller board, and the like.

  The controller can control all of the operations of the deposition apparatus. The system controller runs system control software including an instruction set that controls timing, gas mixing, chamber pressure, chamber temperature, wafer temperature, RF power level, wafer chuck or pedestal position, and other parameters of a particular process To do. In some embodiments, other computer programs stored in the memory device associated with the controller may be used.

  In general, there is a user interface associated with the controller. The user interface may include a display screen, graphical software display of equipment and / or process conditions, and user input devices such as a pointing device, keyboard, touch screen, microphone, and the like.

  Computer program code that controls deposition and other processing in the process sequence may be written in, for example, assembly language, C, C ++, Pascal, Fortran, or any other conventional computer readable programming language. Compiled object code or script is executed by the processor to perform the tasks identified in the program.

  The controller parameters relate to process conditions such as, for example, process gas composition and flow rate, temperature, pressure, RF power level, plasma conditions such as low frequency RF frequency, cooling gas pressure, and chamber wall temperature. These parameters are provided to the user in the form of a recipe and can be entered using a user interface.

  The signal to monitor the process may be provided by the system controller's analog and / or digital input connections. Signals that control the process are output to the analog and digital output connections of the deposition apparatus.

  System software can be designed or configured in many different ways. For example, various chamber component subroutines or controlled objects may be written to control the operation of the chamber components necessary to perform the deposition process of the present invention. Programs or program sections for this purpose include substrate positioning code, process gas control code, pressure control code, heater control code, and plasma control code.

  The substrate positioning program includes program code that controls chamber components used to place the substrate on a pedestal or chuck and control the spacing between the substrate and other parts of the chamber such as the gas inlet and / or target. sell. The process gas control program may include code for controlling the gas composition and flow rate prior to deposition and optionally forcing gas into the chamber to stabilize the pressure in the chamber. The pressure control program may include code that controls the pressure in the chamber, for example, by adjusting a throttle valve or the like in the chamber exhaust system. The heater control program may include code that controls the current to the heating unit used to heat the substrate. Alternatively, the supply of a heat conduction gas such as helium to the wafer chuck can be controlled.

  Examples of chamber sensors that can be monitored during deposition include pressure sensors such as mass flow controllers, manometers, and thermocouples placed on pedestals or chucks. Appropriately programmed feedback and control algorithms can be used along with data from these sensors to maintain the desired process conditions.

Thus far, the implementation of the embodiments of the present invention in a single or multi-chamber semiconductor processing tool has been described.
[Usage]

  Embodiments of the present invention can be used to deposit low resistivity tungsten films for many different applications. One suitable application is interconnects in integrated circuits such as memory chips and microprocessors. An interconnect is a current line found in a single metallization layer and has a generally long thin flat structure. These are formed by blanket deposition of a tungsten film (by the process as described above), followed by patterning to locate the current tungsten lines and removing tungsten from the regions outside the tungsten lines.

  A major example of interconnect applications is bit lines in memory chips. Of course, embodiments of the present invention are not limited to interconnect applications, and extend to vias, contacts, and other tungsten structures commonly found in electronic devices. In general, embodiments of the invention find application in any environment where a low resistivity tungsten film is required. Another major example is contact vias.

  Embodiments of the present invention also focus on relatively thin, low resistivity tungsten films, typically on the order of 500 angstroms or less, preferably 300 angstroms or less. More generally, however, embodiments of the present invention apply to a wider range of tungsten films, including tungsten films having a thickness of about 5 angstroms to 1000 angstroms. Generally, it is 2000 to 3000 angstroms, but a thick film of about 4000 angstroms can be deposited. These thick films (2000 to 4000 angstroms) are typically used for plug fill or plug fill and one metal line, while thinner films are used for bit lines. In general, the film thickness depends on the specific integration scheme.

  8A and 8B are cross-sectional views showing two different laminated films that can be formed using the method of the present invention. Both laminated films can represent interconnect applications as described above. The stacked film of FIG. 8A is formed on the underlying substrate 801 and may be a single component or, more generally, a composite multifunction structure having various conductive, insulating, and semiconductor components. For example, the substrate 801 can have a top layer comprising silicon or a dielectric such as silicon dioxide. The substrate 801, the titanium layer 803, the titanium nitride layer 805, the tungsten nucleation layer 807, and the tungsten bulk layer 809 are in contact in this order (formed according to the embodiment of the present invention). The titanium layer 803 is generally deposited by a CVD process, so that fairly good adhesion with the lower substrate 801 can be obtained. Titanium nitride layer 805 is typically deposited using CVD or PVD methods and is used to prevent exposure of the underlying titanium and / or silicon to tungsten hexafluoride during subsequent tungsten deposition. WF6 is known to be very strong with titanium and sometimes reacts dramatically. The tungsten nucleation layer 807 is preferably formed by a pulse nucleation process. The tungsten bulk layer 809 is formed according to the embodiment of the present invention as described above. In interconnect applications as described above, layers 803, 805, 807, and 809 are all etched to form interconnect lines.

The stacked film of FIG. 8B is similar to FIG. 8A in that there is a lower substrate 811 (eg, containing silicon and / or silicon dioxide), a tungsten nucleation layer 815, and a tungsten bulk layer 817. However, a tungsten layer 812 and a tungsten nitride layer 813 are used instead of the titanium and titanium nitride layers. Nitride layer 813 is used to prevent the underlying silicon from being exposed to WF6 and is generally deposited using CVD or PVD to provide fairly good adhesion to the underlying silicon or dielectric substrate. Provides high quality, but does not necessarily provide a high quality layer sufficient to function as an interconnect. In the laminated film of FIG. 8A, all of the layers 812, 813, 815, and 817 are etched to form an interconnect line.
[Other Embodiments]

  Although the invention has been described with respect to several embodiments, there may be alterations, modifications, substitutions, and alternative equivalents, which are within the scope of the invention. It should be noted that there are many alternative ways of implementing the method and apparatus of the present invention. Accordingly, the appended claims are intended to be construed to include all such alterations, modifications, substitutions and alternative equivalents as fall within the true spirit and scope of the embodiments of this invention. The

  So far, embodiments of the present invention have been described that form a tungsten thin film with low resistivity and excellent uniformity and adhesion. The method described in the present specification can also be applied to form other metal films including copper and aluminum with low resistivity and excellent uniformity and adhesion.

Claims (18)

A method of forming a tungsten film on a substrate in a reaction chamber,
(A) placing the substrate in the reaction chamber;
(B) depositing a tungsten nucleation layer on the substrate;
(C) exposing the nucleation layer to a plurality of reducing agent pulses, wherein there is no pulse action between the pulses;
(D) depositing a tungsten bulk layer on the tungsten nucleation layer to form the tungsten film;
A method comprising:   The method of claim 1, wherein the reducing agent is a boron-containing reducing agent.   The method of claim 1, wherein the reducing agent is diborane.   The method of claim 1, wherein the number of reducing agent pulses in step (c) is 2-8.   Prior to step (c), the method further comprises the step of heating the substrate to about 375 ° C. to 415 ° C. to stabilize the temperature, wherein the temperature is maintained at about 375 ° C. to 415 ° C. during step (c). The method of claim 1, wherein:   The method of claim 1, further comprising heating the substrate to about 375 ° C. to 415 ° C. prior to step (d).   The method of claim 1, further comprising exposing the nucleation layer to a tungsten-containing precursor prior to step (d).   The method of claim 1, wherein each pulse of the plurality of reducing agent pulses in step (c) has a pulse time, the pulse time being about 0.5 to 5 seconds.   The method of claim 1, wherein each pulse of the plurality of reducing agent pulses in step (c) has a pulse time, and the pulse times of at least two reducing agent pulses are different.   The method of claim 1, wherein the interval between reductant pulses in step (c) is about 2 to 5 seconds.   The method of claim 1, wherein the interval time between reducing agent pulses in step (c) is different in at least two interval times.   The method according to claim 1, wherein the interval time between reducing agent pulses in step (c) is shorter for subsequent pulses.   The method of claim 1, wherein each pulse in the plurality of reducing agent pulses has a flow rate, and the flow rate is approximately 100 to 500 sccm.   The method of claim 1, wherein each reducing agent pulse in the plurality of reducing agent pulses has a flow rate, and the flow rates of at least two reducing agent pulses are different.   The method of claim 1, wherein a percent of sheet resistance non-uniformity of the tungsten film formed on the substrate is less than 5%.   The method of claim 1, wherein the resistivity of the tungsten film formed on the substrate is less than about 15 micro ohm centimeters for a 500 angstrom thick tungsten film. A method of forming a tungsten film on a substrate in a reaction chamber,
(A) placing the substrate in a reaction chamber;
(B) depositing a tungsten nucleation layer on the substrate by a pulse nucleation layer process;
(C) heating the substrate to about 395 ° C. to stabilize the temperature;
(D) exposing the nucleation layer to 2 to 8 pulses of diborane while maintaining the substrate temperature at about 395 ° C., wherein there is no pulse action between the pulses;
(E) maintaining the temperature of the substrate at about 395 ° C .;
(F) exposing the nucleation layer to a tungsten-containing precursor;
(G) depositing a tungsten bulk layer on the tungsten nucleation layer to form the tungsten film;
With
The diborane has a flow rate of about 100 to 500 sccm, a pulse time of about 0.5 to 5 seconds, and an interval time of about 2 to 5 seconds.
Method. An apparatus for depositing a tungsten film on a substrate,
a) a multi-station substrate deposition chamber;
b) a controller for controlling operation in the multi-station deposition chamber;
With
The multi-station substrate deposition chamber comprises:
i) a tungsten nucleation layer deposition station having a substrate support and one or more gas inlets for exposing the substrate to a pulse of gas;
ii) a reducing agent exposure station having a substrate support and one or more gas inlets for exposing the substrate to a pulse of gas;
iii) a tungsten bulk layer deposition station having a substrate support and one or more gas inlets for exposing the substrate to a gas;
Have
The operation controlled by the controller is:
i) forming a tungsten nucleation layer on the surface of the substrate by generating a plurality of reducing agent pulses / purge gas pulses / tungsten-containing precursor pulse cycles in the tungsten nucleation layer deposition station;
ii) generating a plurality of reducing agent pulses at the reducing agent exposure station without pulsing between the pulses;
iii) releasing a tungsten-containing precursor and a reducing agent to the tungsten bulk layer deposition station;
Including the device.